Breakerless ignition system with magneto supply and transistor controls



March 31, 1970 G. STRELOW 3,504,373

BREAKERLESS IGNITION SYSTEM WITH MAGNETO SUPPLY AND TRANSISTOR CONTROLS Filed May 1, 1968 o MB b c f /zf 2 \QNASVT a 5 m 9 1 .6 1 a m a United States Patent US. Cl. 315218 Claims ABSTRACT OF THE DISCLOSURE An ignition arrangement for internal combustion engines in which the ignition coil is mounted upon a ferromagnetic core terminating in two pole pieces. These pole pieces partially surround a permanent magnet which is rotatably driven through the crank shaft of the engine. As a result of the motion of the permanent magnet the amount of flux linking the ignition coil is varied so as to induce periodic impulses in the coil. The spark plug to be fired is applied across the secondary winding of the ignition coil. The primary winding of the coil is connected to an electronic circuit having a plurality of controlled switching elements which may be in the form of transistors. The emitter-collector path of a first one of such transistors is connected in series with the primary Winding and serves to interrupt the primary circuit. The base of this first transistor is connected to the emittercollector path of a second transistor so that the state of the second transistor determines the control potential of the first transistor. The base of the second transistor is A coupled to a resistor-capacitor network which, in turn, is

connected to the primary Winding of the ignition coil. Through rotation of the permanent magnet, the circuit of the primary winding is periodically interrupted so as to induce voltage impulses in the secondary winding for firing the spark plugs. This interruption of the primary circuit is accomplished without the use of any mechanical or movable switching contacts.

BACKGROUND OF THE INVENTION In the ignition arrangement of the present invention, the ignition energy is obtained from a magnetic system which is made movable relative to an ignition coil. At least one spark plug is applied across the secondary winding of the ignition coil. In the primary winding of the ignition coil, a voltage is induced through interruption of the primary winding in a manner requiring no contacts.

The present invention is in the class of magnetic ignition devices which are particularly applicable for powering the ignition arrangement without the use of any battery.

In conventional arrangements for magnetic ignition in internal combustion engines, the opening of the primary circuit of the ignition coil is accomplished through a mechanical interrupting switch which is actuated by a cam rotatably driven by the internal combustion engine. The contacts of the interrupting switch, however, become abraded or pitted and covered with oil films after an extended period of operation. This state of the contacts then results in unreliable operation of the ignition process.

In the German Patent 958,971 a magnetic ignition arrangement is disclosed in which the opening of the primary circuit of the ignition coil is accomplished without any moving contacts. A magnetically controlled semiconductor is provided, in connection with this arrangement, in which the ohmic resistance value is increased at the instant of ignition. Taking into account the structural 3,504,373 Patented Mar. 31, 1970 ICC design of this semi-conductor, the latter is situated in a magnetic circuit. The flux of this magnetic circuit is varied through a movable magnetic member driven by the internal combustion engine. The arrangement is such that when the magnetic flux increases, the resistance magnitude of the semi-conductor increases.

A semi-conductor of this type is very temperature sensitive. However, in view of the condition that it is to be situated in the vicinity of a member moved and coupled by the internal combustion engine, it is necessary to locate the semi-conductor near the engine which becomes considerably heated. The operating characteristics of this semi-conductor are thereby influenced in an undesirable manner, since the ignition process can be commenced at an incorrect instant of time. It is not possible to locate the semi-conductor more remotely from the engine due to the prevailing magnetic stray fields. These stray fields will interfere with the realization of a satisfactory ignition voltage impulse at each time. Aside from this, the generation of the ignition voltage impulse is also influenced in an undesirable manner, since the primary circuit cannot be fully interrupted without the application of further measures. This is because the resistance of such a semiconductor can only be raised to a terminal value through such magnetic effects. As a result, the remaining current is compensated through considerable circuit complexity involving an increased number of circuit elements.

Accordingly it is an object of the present invention to provide an ignition arrangement in which the primary circuit of the ignition coil is also opened without movable contacts, but at the same time avoids the undesirable characteristics of the arrangement known in the art.

The object of the present invention is achieved through the application of a first controlled electronic switch for the purpose of opening the primary circuit of the ignition coil. The switching path of this first electronic switch is connected to a monitoring resistor. This resistor, in turn, is associated with a series circuit comprising a limiting resistor and a controlled capacitor. One terminal or electrode of this controlled capacitor is joined to one terminal of the monitoring resistor, and this junction is also connected to one terminal of the primary winding on the ignition coil. The other terminal of this primary winding is connected to the limiting resistor and the controlled electrode of a second controlled electronic switch. The switching path of this second electronic switch provides the controlled potential for the controlled electrode of the first electronic switch.

SUMMARY OF THE INVENTION An ignition arrangement for internal combustion engines in which the voltage holds for firing the spark plugs of the engine is generated without the use of mechanical or moving contacts. The spark plug is applied across the secondary Winding of an ignition coil. The primary winding of the ignition coil is wound upon the same ferromagnetic core and magnetically linked with the secondary winding. The ferromagnetic core terminates in two pole pieces surrounding a movable permanent magnet. This permanent magnet is mechanically coupled to the crank shaft of the engine and driven thereby. The circuit of the primary winding of the ignition coil includes a first controlled electronic switch which interrupts the primary circuit so as to induce a voltage impulse in the secondary winding. This controlled electronic switch can be in the form of a transistor in which the controlled electrode is the base and the switching path of the transistor is the emitter collector path. The primary circuit of the ignition coil also includes a monitoring resistor which is, in turn, connected to a series circuit consisting of a controlled capacitor and a limiting resistor. One terminal or electrode of the controlled capacitor is connected to the monitoring resistor as well as one terminal of the primary winding. The other terminal or electrode of the controlled capacitor is connected to the controlled electrode of the second controlled electronic switch which may also be in the form of a transistor. The switching path of this second electronic switch or transistor is connected to the controlled electrode of the first electronic switch. As a result, the switching path of the second electronic switch applies controlled potential to the first electronic switch. The arrangement is such that through the action of the rotating permanent magnet, the circuit of the primary winding becomes periodically interrupted without the use of moving switching contacts. The spark plugs applied across the secondary winding thus receive induced voltage impulses with high reliability.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING An electrical schematic diagram showing the electromagnetic members operating in conjunction with the elec tronic switching elements for providing voltage impulses to spark plugs, in accordance with the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawing the ignition energy is derived in the arrangement of the present invention, through the combination of the magnetic system having a permanent magnet 11 moving relative to an ignition coil 12. The magnet 11 is mechanically coupled to the internal combustion engine to a coupling linkage denoted by the dash-dot line 13. By means of this mechanical coupling the permanent magnet 11 is rotated in correspondence with the speed of the internal combustion engine (not shown). The ignition coil 12 is wound upon a ferromagnetic core 14 which is mounted stationarily in relation to the magnet 11. The ferromagnetic core 14 has pole pieces 15 and 16 surrounding partially the magnet 11. The ignition coil 12 has a primary winding 17 and a secondary winding 18. At the output terminals a and b of the secondary coil 18, a spark plug 19 is connected. The essential circuit elements within the primary circuit of the primary winding 17, include a first electronic control switch T and a monitoring resistor 20. The electronic switch T has a switching path through the electrodes K and E The monitoring resistor 20 is connected across a switching path K E of the first electronic switch T The direction of current flow is denoted by J. This denoted direction of effective current flow is to be assumed as that direction in which the current flows when the ignition process is in eifect.

Connected across the monitoring resistor 20, is a series circuit including a limiting resistor 21 and a control capacitor 22. One terminal of the capacitor 22 is joined to one terminal of the monitoring resistor 20, and the junction is, in turn, connected to one terminal c of the primary winding 17. The other terminal of the capacitor 22 is connected to both the resistor 21 and the control electrode B of a second electronic control switch T This second electronic switch has a switching path E K which provides control potential for the control electrode B of the first electronic switch P A switching element 23 is connected across the terminal E of the first electronic switch T and the terminal E of the second electronic switch T This switching element 23 conducts current only when the applied voltage has a predetermined value or level. A Zener diode may, for example, be used for the switching element 23. One or more conventional diodes may, however, be used for this purpose when biased with corresponding threshold voltage.

A protective diode 24 is connected to the terminal 11 leading to the monitoring resistor 20 by way of the primary winding 17. This terminal 11 is also a common terminal for the secondary winding 18. A control resistor 25 is connected between the diode 24 and the terminal K of the first electronic switch T A second control resistor 26 is connected to the electrode E of the second electronic switch T and to the junction between the diode 24 and resistor 25. This junction is denoted by the reference numeral 27. Through this arrangement of the resistor 26 the control potential for the first electronic switch T is derived. The diode 24 serves as a protective means for the ignition arrangement by protecting the latter against inverted operation.

It is of particular advantage to proved a third electronic controlled switch T in conjunction with the second electronic switch T The switching path E K is connected in parallel or across electrodes E and B of the electronic switch T The control electrode B of the third electronic switch T is connected to the junction of resistor 20 and capacitor 22, by way of a switching element 29. This junction of capacitor 22 and resistor 20 is denoted by the reference numeral 28. A switching element 29 becomes conducting only when the applied voltage attains a predetermined value or level. A Zener diode is selected as an example for this purpose. It is desirable to connect a resistor 30 in series with a switching element 29.

The ignition arrangement may be realized in a simple manner by making the first electronic switch T as an npn transistor. The second electronic switch T is in the form of a pnp transistor, whereas the third electronic switch T is also of the pnp transistor type. A resistor 31 is connected across the base-emitter path of the transistor T while a resistor 32 is connected across the baseemitter path of the transistor T These resistors 31 and 32 serve the purpose of establishing the magnitude of the controlled potentials for these transistors T and T By closing the switch 33, the ignition processes for the operation of the internal combustion engine can be initiated.

In operation, the magnet 11 moves with its north and south poles past the pole pieces 15 and 16 and thereby induces an increasing voltage in the ignition primary winding 17. If this voltage is such that it tends to produce current flow in the direction J, then the increase in the voltage results in current flow through the protective diode 24, the second control resistor 26, the control path E -B of the second electronic switch T the limiting resistor 21, and the monitoring resistor 20. This current flow, in this manner functions to open the switching path E -K of the second electronic switch T Through the switching path E K the control potential of the control electrode B of the first electronic switch T is also increased in positive direction. As a result, the switching path K E of this electronic switch T also becomes mildly conducting. Current can thereby also flow through the circuit path established by the protective diode 24, the first control resistor 25, the switching path K E and the monitoring resistor 20. The potential of the junction point 28 is thus made negative, and this negative potential is transmitted, by way of the control capacitor 22, to the control electrode B of the second electronic switch T Accordingly, the circuit path E K of the electronic switch T is brought into the conducting state. Independent of this the switching path K -E of the first electronic switch T is also brought fully into the conducting state.

The control capacitor 22 is designed so that it is fully charged when the current in the primary winding of the ignition coil 12 attains the desired value for realizing the ignition spark. When the control capacitor 22 is fully charged, the potential of the control electrode B of the second electronic switch P increases rapidly in the positive direction. As a result, the switching path E K as well as the switching path K E of the first electronic switch T becomes non-conducting or cut-off. This causes a momentary interruption in the primary circuit of the ignition coil 12. In consequence of this, a high voltage impulse appears in the secondary winding 18 of the ignition coil 12. This high voltage impulse produces an electrical jump at the electrodes of the spark plug 19.

At the instant of interruption, however, the voltage in the primary winding 17 increases rapidly at the same time. It is necessary, therefore, to prevent the second electronic switch T and thereby also the first electronic switch T to again be turned on or brought into the conducting state. The switching element 23 is provided for this purpose.

The instant of ignition is established more precisely through the application of the third electronic swtch T in conjunction with the switching element 29. The switching element 29 assures that the primary circuit is always switched at one and the same magnitude of current. This results from the condition that the switching element 29 monitors the voltage across the resistor 20, which depends upon the current in the primary circuit. At the instant that the predetermined voltage level has been attained, the switching element 29 becomes suddenly conducting. As a result, a negative potential appears at the control electrode B of the third electronic switch T This negative poten' tial causes the switching paths E K of the switch T to be in the conducting state. The control path Eg-Bz of the second electronic switch T is thereby short-circuited, and the switching path Ez-Kg of this switch T is cut-off or turned-off. The same situation prevails for the circuit switching path K E of the first electronic switch T which is also turned-off or non-conducting. This is due to the interruption of the primary circuit of the ignition coil 12, as described above.

If, as a result of slow rotation of the magnet 11, the predetermined voltage level for the switching element 29 is not attained, the control capacitor 22 provides for interruption of the primary circuit. 1

The ignition arrangement, in accordance with the present invention, has the particular advantage that the instant of ignition is automatically advanced wih increase in speed of the internal combustion engine. This is due to the condition that when the rotational speed of the engine increases, the magnitude of the current at which interruption of the primary circuit is depended upon, is more rapidly attained.

The limiting of the current, furthermore, providesfor greater operating safety of the ignition arrangement, since no dangerous excessive voltages can appear. In the exemplary embodiment, the magnet 11 is rotatable and the ignition coil 12 is designed as stationary. It is however considered to be within the frame of the present invention, that the magnet 11 be made stationary and the ignition coil 12 be made rotatable together with its ferromagnetic core 14.

The disclosed embodiment, furthermore, is shown to have only one spark plug 19 within the secondary circuit of the ignition coil 12. It is quite possible to provide also a plurality of such spark plugs which precede their ignit on impulse in predetermined sequence through the application of a conventional ignition distributor.

Electronic vacuum tubes or semi-conductor controlled rectifiers can, furthermore, be provided in place of the transistors T T and T The magnetic system can furthermore, be provided with a plurality of magnets, The design can be arranged so that the magnets are mounted in the form of a conventional rotatable magnetic disc.

It will be understood that each of the elements described above, or two or more together, may also find a.

useful application in other types of ignition arrangement for internal combustion engines, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characterisics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended Within the meaning and range of equiv alence of the following claims.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims:

1. An ignition arrangement for internal combustion engines comprising, in combination, spark plug means to be fired by said ignition arrangement; ignition coil means having a primary winding and a secondary winding, said secondary winding being connected to said spark plug means; magnetic means linked magnetically with said ignition coil means and coupled to said engine so as to be moved relative to said ignition coil means; first controlled electronic switching means having a controlled electrode for controlling the current flow through the switching path of said switching means, said switching path interrupting the circuit of said primary winding; monitoring resistor means connected to the switching path of said first controlled electronic switching means; limiting resistor means and controlled capacitor means connected in series to form a series combination connected to said monitoring resistor means, one terminal of said capacitor means being connected to said monitoring resistor means and said primary winding of said ignition coil means; and second controlled electronic switching means having a controlled electrode connected to said limiting resistor means and the other terminal of said capacitor means, said second electronic switching means having a switching path connected to the controlled electrode of said first electronic switching means and applying controlled potential thereto, so that the circuit of said primary winding of said ignition coil means is interrupted as a function of the motion of said magnetic means.

2. The ignition arrangement for internal combustion engines as defined in claim 1 including a threshold switching means connected to the switching path of said second electronic switching means and conducting cur-rent only when the voltage potential applied to said threshold switching means attains a predetermined level.

3. The ignition arrangement for internal combustion engines as defined in claim 2 including protective diode means connected to said primary winding of said ignition coil means and to the switching path of said first electronic switching means; and control resistor means connected to said protective diode means and to the switching path of said first electronic switching means, said protective diode means and said control resistor means forming a series circuit with the switching path of said first electronic switching means.

4. The ignition arrangement for internal combustion engines as defined in claim 3 including second control resistor means connected to the switching path of said second electronic switching means and to the junction of said protective diode means and said first control resistor means.

5. The ignition arrangement for internal combustion engines as defined in claim 4 including third electronic switching means having a control electrode connected to the junction of said monitoring resistor means and said control capacitor means, the switching path of said third electronic switching means being connected to the switching path of said second electronic switching means and to the control electrode of said second electronic switching means; and auxiliary threshold switching means connected between the control electrode of said third electronic switching means and the junction of said monitoring resistor means and said control capacitor means, said auxiliary threshold switching means conducting current only when the applied voltage potential exceeds a predetermined level.

6. The ignition arrangement for internal combustion engines as defined in claim 5 including scaling resistor means connected in series with said auxiliary threshold switching means.

7. The ignition arrangement for internal combustion engines as defined in claim 3 wherein said first electronic switching means comprises an npn t-ransistor and biasing resistor means connected between the emitter and base of said npn transistor.

8. The ignition arrangement for internal combustion engines as defined in claim 3 wherein said second electronic switching means comprises a pnp transistor.

9. The ignition arrangement for internal combustion engines as defined in claim 5 wherein said third electronic switching means comprises a pnp transistor and biasing resistor means Connected between the emitter and base of said pnp transistor of said third electronic switching means.

10. The ignition arrangement for internal combustion engines as defined in claim 1 wherein said magnetic means comprises a permanent magnet rotated by said engine and varying the flux linkages through said ignition coil means.

References Cited UNITED JAMES W. LAWRENCE, Primary Examiner C. P. CAMPBELL, Assistant Examiner US. Cl. X.R. 315-205; 123-148 

